Abstract
BackgroundPhalaenopsis is one of the important ornamental plants worldwide. It plays the most significant role in flower exportation in Taiwan. However, the yellow leaf disease caused by Fusarium spp. has reduced the orchid flower yield 10–50 % yearly. Varieties resistant to yellow leaf disease associated with Fusarium is urgently needed for orchid growers and breeders, and is the ultimate solution for the long-term goal. To achieve this, phenotyping is the first step and the most necessary information for further studies, such as resistance gene identification, quantitative trait loci identification, and genome-wide association study.ResultsThe inoculation of Fusarium was performed in either abbreviated stem or detached leaf, and the pros and cons were compared. The former is the general method of phenotyping for estimating the tolerance to yellow leaf disease of Phalaenopsis, but it is time-consuming and spacy, and thus not suitable for the assessment of large numbers of samples. In contrast, the latter not only showed a similar trend of disease severity with time reduced to only one fourth of the former one but also less space needed.ConclusionsThis solution allows a better phenotyping approach for the fast detection of yellow leaf disease associated with Fusarium in a large number of Phalaenopsis samples.
Highlights
Phalaenopsis is one of the important ornamental plants worldwide
The disease severity level (DSL) was ranked as followed: Level 0: no symptom; level 1: number of black holes less than 3; level 2: number of black holes between 4 and 7; level 3: black holes connect together; level 4: black lesion spreads outside of the wound; level 5: less than 3 holes filled by the hypha from F. solani; level 6: 4 to 7 holes filled by hypha from F. solani; level 7: the hypha mixed together; level 8: yellow symptom emerges; level 9: yellow symptom diffuses to an entire detached leaf or abbreviated stem; level 10: the red spores show (Figs. 1 and 2)
These DSL levels were applied to the photos taken from all five varieties, and three replicates for calculating the Disease severity index (DSI) of different tissues
Summary
Phalaenopsis is one of the important ornamental plants worldwide It plays the most significant role in flower exportation in Taiwan. The yellow leaf disease caused by Fusarium spp. has reduced the orchid flower yield 10–50 % yearly. In Taiwan, the export value of Phalaenopsis in 2019 was about 140 million US dollars which covered 75 % of the total value of orchid exportation (https://www.coa.gov.tw/).Fusarium spp., pathogens damage crop widely and cause up to 50 % yield loss in soybean, banana, tomato, and wheat (Perincherry et al 2019). The fungicides showed effect to inhibit the mycelial growth of Fusarium (Su et al 2014), none of them show significant effects on the reduction of the damage caused by F. solani in the greenhouse environment (Su et al 2014), or after a long
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